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Optimizing nutrient delivery in greenhouse-grown potted chrysanthemums

Posted on January 30, 2022February 2, 2022 by Rita Weerdenburg

30
Jan

The ever-increasing cost of fertilizer inputs is just one reason why growers of agricultural and horticultural crops in both outdoor and controlled greenhouse growing environments have found it necessary to take a closer look at their application rates and practices. Across Canada, the horticultural sector and especially greenhouse growers have come under additional scrutiny as the possible source of contamination when unacceptable levels of pollutants have been found in nearby streams and ponds. Just as critical, therefore, has been the need to meet increasingly stringent regulations set by environmental agencies to control the quality of irrigation run-off water.

As a result, researchers are now looking to answer the seemingly simple question of “how low can you go,” as part of the solution to both dilemmas which currently face the floriculture greenhouse grower.

A research project currently underway by the University of Guelph’s Dr. Barry Shelp, “Optimizing nutrient delivery in greenhouse-grown potted chrysanthemums: Sub-irrigation and drip irrigation systems” tests the hypothesis that nutrient use can be vastly improved by strategically manipulating the timing of nutrient delivery to the plant. This project is part of the “Accelerating Green Plant Innovation for Environmental and Economic Benefit” Cluster and is funded by the Canadian Ornamental Horticultural Alliance (COHA-ACHO), private sector companies, and the Government of Canada under the Canadian Agricultural Partnership’s AgriScience Program, a federal, provincial, territorial initiative Dr. Shelp’s current project is specifically focused on testing the improved delivery of micro-nutrients to both drip irrigated and sub-irrigated chrysanthemums.

Dr. Barry Shelp
University of Guelph

Commercial trials with different N (left) and NPK (right) rates.

The current project is a continuation of his previous research project under the Growing Forward 2 (2013 – 2018) Cluster program which demonstrated the successful reduction of macronutrient use. In that project, Dr. Shelp was able to verify that the supply of nitrogen, phosphorous, sulfur and potassium could be reduced by as much as 75 to 87.5% compared to current industry standards, without any adverse impacts to crop yield or quality.

The overall premise of his current research, says Dr. Shelp, to test the limits of lowering fertilizer inputs seems very simple. However, far more complex is the understanding of plant physiology and using a plant’s inherent capacity and attributes to inform the decision-making processes about fertilizer application which has shaped the foundation of his hypothesis.

“For many years, and even as a post-doc, I began to understand and marvel at plant characteristics associated with nutrient acquisition and redistribution in the plant. I came to realize that a plant’s source of nutrition changes as the plant grows and develops and if proven to be true, that premise could greatly influence commercial fertilization practices. Although that was many years ago, I am grateful for the circumstances that are finally giving me the opportunity to test my theory.”

Articulating his hypothesis in simple terms, Dr. Shelp explains that young plants absorb nutrients through the root system, but that changes as the plant matures. Plants then start to use previously acquired and stored nutrients and use them for fruit and flower development. By strategically lowering the nutrition rates, plants can be induced to better absorb nutrients early in the growth cycle and to redistribute their stored resources later in the growth cycle to supply the reproductive parts of the plant.

Rather than continuously supplying a plant with nutrients, Dr. Shelp’s theory calls for an interruption to fertilizer application at a time in a plant’s growth cycle when it has sufficient stored nutrients in the leaves to sustain reproductive growth. Typically, the time is best at the onset of flowering, when the plant transitions from vegetative to reproductive growth, is most efficient at mobilizing nutrients, and the uptake of nutrients through the root system starts to decline. Remarkably, this procedure can be combined with a reduction in nutrient supply to the young plants, and as long as it not excessive, the efficiency of nutrient uptake by the roots is improved so that the plant acquires and stores the same amount of nutrients as with a much higher nutrient supply.

Research trials with different Fe (left) and Zn (right) rates.

Dr. Shelp recognizes the challenges associated with grower adoption of new technologies and growing practices. “Once growers have a formula that works for them, it is understandable that change poses a huge risk.” He is nonetheless confident that it is only a matter of time before growers slowly implement the new and reduced fertilization guidelines based on his research results.

It is a very simple matter to quantify the savings that can be realized through less fertilizer use. It is more difficult to quantify the savings that can be achieved through reduced costs associated with cleansing spent irrigation water, and especially the run-off that occurs with drip irrigation. “It’s difficult to put a value on being able to meet the strict regulations set by environmental agencies, but growers instinctively recognize the benefits are significant.”

Conducted at both the University of Guelph’s experimental greenhouse labs and a Niagara-based commercial greenhouse grower, Dr. Shelp’s research focused on chrysanthemums, using four commonly grown varieties, as they are the largest dollar volume greenhouse floriculture crop grown in Canada. Crops were measured for yield and overall plant quality and nutrient leaf analysis by the University’s Laboratory Services division was used to provide information on the level of micronutrients. To date, Dr. Shelp has worked with sub-irrigation systems because if managed properly, the composition of the excess nutrient solution is essentially unchanged, so it can be recycled and reused. However, he intends to also test his modified delivery strategy with drip irrigation because of its importance in the industry. If the nutrient supply can be reduced, then it should be possible to reduce the overirrigation that is required to prevent salt accumulation in the growing medium, thereby conserving both nutrients and water.

After research validating his theory on the reduced use of macronutrients (nitrogen, phosphorous, potassium, calcium, magnesium and sulfur), Dr. Shelp set out to study the impacts of reducing the use of micronutrients. In separate trials, the project looked at zinc, copper, iron, manganese, boron and molybdenum. Depending on the formulation of the comparative commercial formulas being studied, results showed that delivery of these nutrients can be reduced by 85-95% over the crop cycle without sacrificing plant and flower quality.

The significance of the research results, says Dr. Shelp, point to several logical “next-step” applications, including outdoor production of ornamental floriculture crops and possibly controlled environment production of edible crops.

Optimized macronutrient delivery during vegetative growth.

Acceptable leaf macronutrient status with optimized delivery during vegetative growth.

Flower development unaffected by Mn nutrition during vegetative growth.

Flower development unaffected by Fe nutrition during vegetative growth.

Optimization of micronutrient delivery during vegetative growth.

Acceptable leaf micronutrient delivery during vegetative growth.

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Understanding how temperatures within plants affect their growth

Posted on July 20, 2021August 29, 2023 by Rita Weerdenburg

20
Jul

A Canadian research project the first of its kind in the world

In much the same way as a greenhouse can trap the sun’s energy, many plant shapes and structures are also able to capture solar energy. Air temperatures inside open bowl or parabolic-shaped flowers, for instance, such as poppy, buttercup or anemone can be several degrees higher than the ambient air temperature. The pubescence of willow catkins and similar plants can trap heat. And air temperatures inside enclosed flowers such as snap dragons can be as much as seven degrees Celsius warmer than the surrounding air temperature.

There is documentation to support the fact that these phenomena as related to floral structures have been observed as early as the 18^th century. More recently, advances in technology have also shown that hollow plant stems also create a greenhouse effect, resulting in increased temperatures inside these stems. While there has been significant research on how ambient temperatures impact plant growth, there is little known about temperature variations caused by plant shape, and especially within hollow stems and other structures can impact plant development.

The research project “Temperatures within horticultural plants: Stems and flowers, explaining rapid growth,” by Dr. Peter Kevan (University of Guelph) and Masters’ graduate student Charlotte Coates, is studying how the micro-thermic regimes in floral stems and flowers may lead to practical applications in culture, aesthetics, and possibly even disease and pest control.

According to Dr. Kevan this is a very specialized area of research and the first of its kind in the world. “We understand the greenhouse effect in broad terms, but there is not a lot of information on micro impacts. The greenhouse is a large model, but even in such protected environments there is an incomplete ability to control many aspects of the environment.” It is suggested by Dr. Kevan and his team that the inter-relationships between the many factors at the macro-level (greenhouse) can be refined to apply at the within-plant micro level as they actually impact plant, growth maturation, reproduction and health.

Simply stated, says Dr. Kevan, a micro thermic regime is what is available in a very small space (micro = small, thermic = warmth or temperature and regime = environment). Focusing on the greenhouse floriculture sector, this research project is studying the impact of temperature variations caused by the micro-greenhouse effect inside hollow stems and other plant parts of both indoor and outdoor plants.

“We were fortunate that the original design of this project included both greenhouse and outdoor production,” noted Charlotte, explaining that the research team were able to continue their work in 2020 and into 2021 in the outdoor environment with some extra COVID protections in place.

Dr. Peter Kevan

University of Guelph

Charoltte Coates

Masters’ graduate student

Figure 1. Pumpkin (Cucurbita pepo L.) flower, top image taken using Forward Looking Infrared Camera that shows a thermal image of the surface temperature of the flower. The scale bar indicates what temperature (°C) each colour in the image matches to.

In the outdoor environment, various squash plant varieties as well as some native plants such as milkweed are good candidates to produce extensive data which can be further analyzed to determine the impact of both temperature and light on plant stem growth and seed development, with results to be translated to indoor production. This outdoor research work is mostly conducted on private lands with the support and interest of co-operator growers in the areas of Guelph, Cambridge, KW, Peterborough and as distant as the Laurentians in Quebec.

Regrettably, some of the preliminary work which was conducted at the UofG greenhouses was lost as COVID access restrictions prevented the team from being able to monitor or maintain their initial research trials. Regardless, Dr. Kevan is confident that the remaining two years of the research project will nonetheless produce some interesting and ultimately useful results.

Although perhaps not overly sophisticated by today’s standards, it is largely due to the specialized high-tech equipment available to the research team that makes it possible to consider this project’s objectives and design.

Figure 2A. Gerbera daisies (Gerbera jamesonii) grown at Van Geest Brothers Greenhouse in Grimsby, ON, with dataloggers recording the ambient air temperature and stem temperature. The study plot contained Gerbera plants with varying degrees of hollowness, and the results showed that hollow Gerbera stems reached more extreme temperatures, both hotter and colder, than the solid stemmed Gerbera.

Figure 2B. Gerbera – Prestige variety with fine wire thermocouple inserted into the stem recording the internal stem temperature, and one secured to the outside of the stem to record air temperature.

Thermocouples — temperature probes made from a pair of very fine wires, are used to measure the internal temperature of plant stems, in flowers and fruits. Battery powered datalogging hand-held units are able to monitor up to eight plants per unit for up to a week at a time. In the outdoor environment, radiation shields eliminate the impact of radiant heat from the sun, so that internal temperatures can be accurately compared to ambient temperatures.

Solar radiation meters are used to collect data on the incident amount of radiation. Spectrometers characterize the type of light that is present. Connected to a computer, they can produce a graph of the visible light spectrum and how much of each wavelength of light is present both outside and inside the plants’ hollow structures.

Thermal cameras are used to accurately measure plant surface temperature. “Thermal cameras have become an important tool for many greenhouse growers,” notes Charlotte, “but the less expensive models used by growers do not always provide completely accurate data. One of the objectives of this project has been to provide growers with data they can use to better interpret their own thermal camera readings.”

Designed to be of benefit to commercial floriculture greenhouse growers, with an initial focus on high value gerbera production, research trials are currently underway thanks to the generous cooperation of a Grimsby, Ont.-based greenhouse grower. Additionally, there is an expectation that the research results will also be of considerable interest to the edible horticulture sector. Some preliminary but not yet documented observations on the impact of temperature variations inside hollow plant parts have been noted in greenhouse grown bell peppers in a cooperator operated greenhouse in Kingsville, Ont.

Figure 3A & 3B. Various colours of snapdragons (Antirrhinum majus) growing in the experimental greenhouse at the University of Guelph. Temperatures within the enclosed petals of the flowers are up to 4.5 ˚C warmer than ambient air.

The team’s work in the outdoor environment has also pointed to a tie-in to research work underway to preserve the pollinator populations, noted Charlotte. Floral temperatures influence pollinator behaviour, as well as floral humidity, presentation, fertilization and seed production. Using micrometeorological techniques in various part of plants allows for deeper insight into how temperature affects pollinator and plant relationships. This is especially important to consider for phenology, as plants and pollinators are dependent on each other to be there simultaneously. Thus, it is understandable that temperature regimes affect pollinating systems in concert with one another rather than on plants and pollinators separately.

Kevan writes: “I am grateful to COHA for their support of a project that I know many people may consider to be a little outside the norm, but I believe the findings of this and follow-up research work will put Canada on the map. Already we have garnered interest from the science community around the world, including U.S., Russia, Australia, Europe and India.”

Figure 4 (top or left): Infrared image of Gerbera flowers from Van Geest Brothers Greenhouse. Average surface temperature of flowers: 22.5 C, the average surface temperature of stems: 20.7 C, and average surface temperature of leaves: 20.1 C. (Right or bottom): Colour image of the study flowers.

This project is part of the “Accelerating Green Plant Innovation for Environmental and Economic Benefit” Cluster and is funded by the Canadian Ornamental Horticulture Alliance (COHA-ACHO), private sector companies, and the Government of Canada under the Canadian Agricultural Partnership’s AgriScience Program, a federal, provincial, territorial initiative.

Irrigation efficiency in nurseries: towards a more sustainable approach

Posted on March 24, 2021August 29, 2023 by Rita Weerdenburg

Optimal irrigation for model species. Laval University Nursery.

24
Mar

Dr. Charles Goulet

Aided by an abundance of research, nursery container production has matured significantly over the years, resulting in ever-increasing categories and size ranges of plants grown in containers. While we have also seen corresponding improvements in irrigation technologies in that same timeframe however, the complexity of containerized nursery production means that nursery growers in Canada continue to rely on inefficient overhead irrigation practices.

The constant movement of pots, necessitated by a multitude of factors ranging from decreased inventory during the sales season to winter storage requirements, adds to the already higher costs associated with more efficient drip irrigation technologies. Additionally, the lack of automation typically available for overhead systems means that watering decisions are based primarily on timed irrigation intervals and visual clues to plan irrigation scheduling. The result can be either under or over watering, both of which can have detrimental impacts on plant growth and quality. More recently, reliable access to water has also become problematic for many growers, making water conservation an increasingly important priority.

A research project currently underway by Laval University’s Dr. Charles Goulet entitled Irrigation efficiency in nurseries: towards a more sustainable approach, will offer nursery growers the ability to optimize their irrigation practices by delivering the right amount of water at the right time and to the right plant. This project is part of the “Accelerating Green Plant Innovation for Environmental and Economic Benefit” Cluster and is funded by the Canadian Ornamental Horticulture Alliance (COHA-ACHO), private sector companies, and the Government of Canada under the Canadian Agricultural Partnership’s AgriScience Program, a federal, provincial, territorial initiative.

This current project continues work started by Dr. Goulet under the Growing Forward 2 (2013 – 2018) Cluster program which focused on the use of wireless tensiometers to measure the water available to the plant, thereby allowing for precise irrigation scheduling based on plant needs. This high-tech wireless web-based technology was paired with drip irrigation systems, with or without capillary mats. Both water use and plant growth were measured to determine the impact of each strategy. The researchers were able to conclude that precision irrigation has the potential to significantly reduce water use in nursery plant production as wireless tensiometers provide reliable data to guide irrigation scheduling decisions. Additionally, wireless technology provides considerable operational flexibility by providing the grower with easy access to data.

Optimal irrigation with automation at the commercial nursery site.

A plant’s water needs can vary widely from species to species, however monitoring the individual needs of each species with tensiometers would be both complicated and expensive. As a result, finding plants with similar watering requirements which can be grouped or clustered in the nursery environment became an important component of this phase one research project. To facilitate the decision-making process on watering practices, such as frequency and volume of water, a series of reference plants representing a good diversity of watering requirements, was determined. As well as being an essential part of the research process, reference plants facilitate the ability for clustering plants according to their very specific cultural requirements.

Initial research was conducted at the University’s production facilities, which incorporates the use of wind tunnels to mitigate as much as possible the impacts of weather events such as rain, temperature and wind, to the research data. However, as the project was eventually moved to a commercial nursery setting, it became necessary to make several modifications to the project’s overall design. The use of wireless tensiometers provided reliable data to the nursery and the research teams, but the challenges associated with weather factors, especially wind or the knowledge of a pending rain event, ultimately pointed to the option of adopting a hybrid approach to irrigation scheduling. Ultimately, the final decision to irrigate was made by the nursery’s production team, guided by data provided by the tensiometers.

Clustering experiment at Laval University Nursery.

The data collected and lessons learned from the first phase of this research project have largely dictated the design and objectives of the current phase. According to Dr. Goulet, “Due to cost factors, nursery growers will find it necessary to use overhead irrigation systems, but there is a need for precision irrigation management that will allow growers to make the most of their existing systems. To be truly efficient in terms of water use, the different irrigation strategies need to be expanded to meet the requirements of the species and the climate.”

The first objective of the current project is to improve irrigation management in the nursery setting through the use of wireless tensiometers. Specifically, the research will seek to optimize the use of tensiometers to support the practice of clustering. The research will also evaluate how the amount and frequency of watering can influence plant growth. Using several species with very diverse watering requirements, in combination with different irrigation management strategies, (eg: comparing different volumes of water and different irrigation intervals) will help researchers to determine water use and the impact on plant growth. More precise data will be obtained in the first two years by conducting the experiment at the Laval University research facilities and the data obtained will be used to determine irrigation strategies when the research is transferred to a commercial nursery setting.

Soil tension measurement at the commercial nursery site.

Research will also continue into expanding the use of clustering practices. In order to best meet the very diverse watering needs of the very wide range of species that make up the inventory of most growers, the number of reference species will be increased. According to Dr. Goulet, “The clustering process is not as simple as it seems, as the factors that impact overall plant growth include factors such as frequency of watering as well as amount of water applied with each irrigation event. Clustering is not as straightforward as determining plant species with high, medium and low water requirements.”

It will be the objective of the project to increase the list of reference species from the current 10 to a total of 15 species, and the corresponding clustering recommendations will be increased from 50 to 100 species. To ensure accurate data, this component of the research project will use the wind tunnel facilities at Laval University to mitigate the impacts of natural weather events.

Optimal irrigation for clustering species. This photo shows the irrigation mats which were used in the Cluster 2 project; they are not a part of the current project.

To truly live up to its potential, precision irrigation must be supported by a solid automation process. Over the past few years, many models have been developed that integrate various technologies to optimize the irrigation process and the third objective of this project will determine the most useful parameters to automate irrigation in the commercial nursery setting. The research team will evaluate if irrigation controlled by evapotranspiration measurements will provide similar results to irrigation controlled by the new generation of wireless tensiometers, as well as the potential to integrate these technologies.

Again looking at the need to provide practical recommendations for use in the commercial nursery setting, the research will evaluate the various parameters which could be added to the automation process with data obtained from external weather sites, including daily rain forecast, wind speed (to delay a planned irrigation event if the wind is too strong) and evapotranspiration predictions. The ultimate goal is to provide growers with various options depending on their existing systems and their resources to acquire new irrigation technologies.

Weather station for irrigation automation.

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New research project focuses on improving standards for effective pond management

Posted on December 11, 2020August 29, 2023 by Rita Weerdenburg

One of five mesocosms or in-pond cells, is installed at a nursery location in the summer of 2019.

11
Dec

Nursery growers have implemented a variety of solutions, with varying degrees of success, to reduce the excessive biological growth usually found in recycled water irrigation ponds. This growth is responsible for the clogging of intake filters and subsequently, expensive maintenance costs. With little in the way of research or scientific data to support alternative methodologies and no clear standards of practice for effective pond management, there is a critical need in the sector for reliable information on affordable and sustainable solutions to improve water quality.

Several projects focusing on water quality are currently being funded through the COHA research cluster. Minimizing horticultural impacts on surface water quality to encourage re-use through enhanced pond management is one of these projects being led by Dr. Jeanine West of PhytoServ. With an end goal of helping growers to manage their irrigation costs through environmentally appropriate and sustainable improved pond management strategies, this project is part of the Cluster Project and is funded by the Canadian Ornamental Horticulture Alliance (COHA-ACHO) and by the Government of Canada under the Canadian Agricultural Partnership’s AgriScience Program

A YSI meter or Sondes probe is used to test and record various parameters such as temperature, pH levels, oxygen levels, turbidity and conductivity in each of the mescosms.

Technicians conduct water sampling at another nursery location.

According to Dr. West, “Almost all nursery growers use recycled water and it is inevitable that they experience issues related to excessive growth of aquatic weeds, algae and cyanobacteria, also known as blue green algae, especially in the warmer summer months. This research project will focus on investigating new methods of controlling the flow of nutrients and especially phosphorous into ponds, and to study various in-pond treatments to improve overall water quality.”

The research project has been designed to take into consideration the requirements of three very diverse audiences. The general public’s increasing concern for the environment is further reinforced by the aesthetics and risks of algae and cyanobacteria in our ponds and lakes. Various ministries across Canada, at both the provincial and federal levels now have in place application and discharge regulations to control the excessive use of nutrients, especially phosphorous and nitrates. And farmers have a need for effective and sustainable pond management strategies that will help them to meet environmental regulations while at the same time mitigating the costly impacts from clogged irrigation systems.

The first phase of the project, completed in 2019 with considerable input from a Technical Advisory Committee, was to design, construct and test a reliable experimental design which would allow for effective comparisons of various water quality treatments. “Arriving at a suitable project design was no easy task,” explains Dr. West, “as it needed to be bigger than a bench scale design, but we had physical and budgetary constraints to consider as well.”

A total of five nursery locations across Ontario were selected as research sites and each one brings unique site challenges and therefore opportunities to the project. “As we’ve come to expect, each of the participating nurseries have been very cooperative in helping us to install the various on-land or in-pond structures necessary for this project,” notes Dr. West adding that several nursery sites have assisted in the installation of media beds to study the impacts of pre-pond treatments.

With a stated objective of employing a systematic evaluation and comparison of various pond management tools, the project devised by Dr. West and her research team consists of up to five mesocosms (in-pond enclosures, or test cells) at each test location. Each mesocosm has a volume of 1-2 m³ (depending on the pond depth), is framed with PVC tubing to allow for flotation, as it was important that water be able to flow around the sides and bottom of each cell. The wall material eventually chosen by the advisory team is a plastic material commonly used as a wind barrier. “Our technical advisory team struggled with the concept of permeability and its ultimate impact on project results. We ultimately determined that the most accurate data would be realized by a limited exchange of water between the mesocosm and the pond water.”

At each site, the project is designed to test up to five mesocosms including a control, and up to four of the following treatments: submerged aquatic macrophytes, aeration through mechanical bubblers, a phosphorus-binding media, vegetative shade through the use of duckweed, and mechanical shading through the use of shade cloth.

Installation of pre-pond media beds.

PhytoLinks™, small constructed floating plant islands, installed in a nursery pond.

At one farm, the research team has also installed a series of PhytoLinks^™, or floating planted islands which, similar to constructed wetlands, are specifically engineered to improve water quality. The PhytoLinks™ were installed in channels within a narrow pond, with one channel empty (control), one with two PhytoLinks™, and one with two PhytoLinks™ and a suspended material that serves as a surface for growth of periphyton, a complex microorganism population known to assist in nutrient uptake.

Any research project conducted in outdoor environments is subject to many unpredictable variables and Dr. West and her team have encountered the usual challenges. With several of the research sites being located far from reliable electrical sources, Dr. West found herself becoming an expert in the design and installation of small solar systems to power an aerator.

The base of a Phytolinks™ constructed floating wetland.

grass-like plants growing in a murky pond

Outdoor research is invariably impacted by adverse weather conditions. A very hot and dry summer resulted in severely reduced water levels, and a less than favourable growing environment for the Phytolinks™ installation.

A mechanical aerator is added to one of the mesocosm.

An exceptionally hot summer in 2020 resulted in excessive water use, impacting the water depth in some ponds. And of course, this year the team found themselves dealing with the ultimate disruptor – the unforeseen impacts of a global pandemic.

As most of the work planned for 2020 has been outdoors and in low-contact environments, Dr. West and her team have been able to successfully mitigate potential impacts of the impacts of Covid19. Working with collaborator Dr. Ann Huber, the team was fortunate to be able employ qualified family members as technicians, making it possible to comply with Covid19 workplace guidelines.

The limited water testing conducted in 2019 was mostly to validate the research design and system installations. Actual water sampling to record and analyze the effectiveness of each treatment, is being conducted throughout 2020 and 2021. A YSI meter or sonde-type multi probe is used to test and record various parameters such as temperature, pH levels, dissolved oxygen levels, chlorophyll a and phycocyanin levels, turbidity and conductivity. Further water and sediment samples are sent to A&L Canada Laboratories to test for nutrient and chemical levels. Grab samples of algae, aquatic plants, and cyanobacteria are collected regularly and diagnosed by Dr. Ann Huber of the Soil Resource Group to look for other trends and indicators of pond health. Some of the most revealing results to date are the inadequacy of water quality indicators in some of the traditional measurements, and the need to explore a range of parameters and testing approaches to truly get a picture of overall pond health.

Confirms Dr. West, “We will share our results with the industry at the end of the season, but with the caveat that there are too many variables at play in any single year, in particular seasonal weather conditions and changes in production practices, to make those results conclusive. Even the two full years of testing we will be able to conduct as part of this project will not be sufficient to provide definitive results but will hopefully point us in the right direction. Ideally, we should be looking at an analysis after five years of testing; hopefully we will be able to extend our experiment past the time restrictions of this research project.”

The research team in 2019 after a successful day of installations.

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Hybrid Treatment Systems show promise as an effective water filtration method for greenhouse and nursery growers

Posted on October 30, 2020August 29, 2023 by Rita Weerdenburg

An in-ground installation of a permanent hybrid treatment system. Advance use of the portable HTS makes it possible to optimize the media sequence specific to each grower’s needs, for the removal of relevant PGRs and pesticides as well as nutrients and fungal populations.

30
Oct

Water recycling is increasingly recognized as necessary to deal with the dual issues of water availability and the ever-evolving environmental restrictions faced by greenhouse and nursery producers related to water run-off. Although conservation has become an essential objective, the practice of using recycled water poses many risks and challenges. Recirculated water often contains nutrient, pesticide and plant growth regulator (PGRs) residues which could negatively affect crop production. Research is being conducted around the world to improve recycled water quality, and several projects currently being funded through the COHA research cluster are especially focused on sustainable and affordable solutions.

Enabling re-circulation with hybrid treatment systems is the next phase of longer-term water research being led by environmental microbiologist Dr. Ann Huber of the Soil Resource Group. This project is part of the Cluster Project and is funded by the Canadian Ornamental Horticulture Alliance (COHA-ACHO) and by the Government of Canada under the Canadian Agricultural Partnership’s AgriScience Program.

Simply stated, a hybrid treatment system (HTS) is a non-vegetated, constructed approach to the filtration and cleansing of water through a series of organic and inorganic media filters. Explains Dr. Huber, “An HTS is the next step in water cleaning technologies as a successor to previous research into constructed wetlands and woodchip bioreactors. While those individual approaches have been found to be useful for some pathogen and nutrient removal, there are many external factors that can impact their usefulness.”

Earlier projects by Dr. Huber have already proven the effectiveness of hybrid treatment systems in the removal of certain nutrients, including nitrogen and phosphorus, and fungal pathogens. The objective of the current project is to expand those research findings to include other greenhouse production chemicals and especially plant growth regulator (PGR) residues, which have been shown to impact plant growth even when found in very low levels of recirculated water.

Due to their typical four- to five-year funding cycle, research projects are generally defined by very specific start and end dates. However, as water issues within the horticulture sector have long been a top priority for both governments and industry, Dr. Huber has succeeded in making her research into effective water re-circulation technologies a mostly continuous long-term field of study, beginning in 2007.

Besides the very obvious benefits of providing the industry with continually updated research results, the continuity of Dr. Huber’s research projects also provides significant economic efficiencies. Two portable pilot units constructed as part of a previous research project funded with support from Flowers Canada Ontario (FCO) at a cost of $50,000 each are now an integral component of this next-phase study.

According to Dr. Huber, “As far as I’m aware, there are no other pilot-scale systems such as these being used for water re-circulation research. The system is designed to have the capacity to test up to eight mineral or organic media in any combination or alternatively, test the same media at different flow rates and retention times. These pilot systems provide us the opportunity to test commercial greenhouse water on-farm without risking the health of the crop.”

The original focus of Dr. Huber’s work was to study the effectiveness of woodchip denitrification bioreactors on the removal of various water pollutants. Although she continues to be optimistic about the use of woodchip as an effective and economical treatment for some contaminants, the current research project also incorporates a number of mineral media, including pea gravel, wollastonite, filter sand and a slag/gravel mix to expand the range of undesirable components that can be removed within a single ‘hybrid’ treatment system.

And, although other researchers are studying organic systems (e.g. woodchips) which employ an aerobic process to remove pesticide and PGR residues, the research work being conducted by Dr. Huber and her research team is an ongoing study of an anoxic approach in order to retain the current treatment system’s capacity to remove nitrogen and fungal pathogens.

With the current research project reaching the half-way mark during the fall of 2020, Dr. Huber and her team have been able to successfully mitigate the impacts of Covid19 that might have otherwise negatively impacted their progress. Most of the work has been outdoors and in low-contact environments, and both Dr. Huber and collaborator Dr. Jeanine West were also extremely fortunate to have access to qualified family technicians.

Although the preliminary research results are not conclusive, to date the data collected by the research team, based on water quality analysis and results of bioassay testing indicate very promising results. The team has been able to demonstrate the removal of a range of PGRs and pesticides by several of the individual media in batch studies, and the bioassay results demonstrate a positive growth response to PGR removal. Interestingly, the bioassay tests are capable of detecting the presence of some PGRs at concentrations lower than the sensitivity of laboratory testing.

Because this is a very new technology, only three growers — two floriculture greenhouses and one nursery grower — are currently using hybrid treatment systems to treat recycled irrigation water. The research team is confident that these early results will meet their original objective, to provide growers with a valuable and affordable approach to realize clean recycled water for their production needs.

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Utilizing high tech to bring native perennials to the marketplace

Posted on July 13, 2020March 10, 2025 by Rita Weerdenburg

13
Jul

Within the ornamental sector, an ever-evolving environmental movement has resulted in the demand for more ecologically responsible plants and plant production techniques. The demand for low-maintenance, drought resistant, low-input plants has converged with the trend to the use of more natives and pollinator plants in our gardens and landscapes. However, as any garden centre owner or landscape designer knows all too well, aesthetic attributes on the sale’s bench or in the landscape plan are all-important. And, from the perspective of greenhouse growers, cost-effective propagation and production technologies are an absolute must if these otherwise desirable plants are to find a way to the consumer’s garden.

Exploring a variety of integrated systems designed to overcome the obstacles that are generally associated with the efficient production of native species, “Integrated techniques for efficient breeding, production and transplant survival of unique ornamental species” is an ambitious research project currently underway at the University of Guelph. This project is part of the Cluster Project and is funded by the Canadian Ornamental Horticulture Alliance (COHA-ACHO) and by the Government of Canada under the Canadian Agricultural Partnership’s AgriScience Program.

Bringing these diverse and lofty goals to this project is achievable largely through a unique collaboration of expertise and facilities. Leading the project, Dr. Alan Sullivan has over 25 years of experience in horticultural breeding with the past 10 years focused on breeding and physiology of native ornamental species that are tolerant to low water and low nutrient conditions.

The project’s co-lead, Dr. Praveen Saxena, has spent 25 years working with stakeholders of the floriculture and horticulture sectors to develop efficient protocols for rapid in vitro multiplication of a diverse range of ornamental and medicinal plants. Dr. Saxena is also the director of the GRIPP Institute, a University of Guelph based organization led by himself and Dr. Sullivan dedicated to the preservation of endangered plant species. GRIPP makes some sophisticated facilities available to this project, including cryopreservation technologies.

With a goal of developing improved varieties and germplasm of existing plant species that already exhibit the required environmental and aesthetic attributes, the project relies on the expertise of Rodger Tschanz, manager of the University’s ornamental trial garden program. Rodger’s many years of on-the-ground supervision of various trial garden programs and other related horticultural projects makes him uniquely qualified to help identify native plants with superior ornamental qualities that are adapted to environmentally challenging conditions.

Focused on two impressive goals – the accelerated breeding and introduction of exiting new perennial plants to the marketplace, together with the development of efficient propagation and production technologies – both Dr. Sullivan and Dr. Saxena are equally excited about the potential economic impact to all sectors of the ornamental industry. “It is our goal to make available to the Canadian ornamental industry a whole new selection of commercially available native plants that support a strong marketplace trend,” said Dr. Sullivan.

Although off to a promising start, keeping the project on track during the COVID-19 shutdown has proven to be a challenge for Dr. Sullivan and Dr. Saxena. “The COVID impacts were severe,” noted Dr. Sullivan. “We are grateful to the University for their positive response to our various applications to continue our research, even on a limited basis, as we had plants that had come out of cold storage and were coming into flower for crossing if we were to keep the project alive and somewhat on track.”

The project team is now coping with a number of unforeseen expenses. Additional greenhouse space is required to accommodate social distancing requirements, and extra costs incurred for more vehicles and trips due to COVID restrictions continue to mount. These unanticipated costs are nonetheless a far better scenario than the alternative of having to start over again.

With some ingenuity and creative solutions, the first objective of the project remains on track. Employing both traditional and advanced breeding methods, new and improved varieties of pre-selected species will be developed and further trialled in the UofG trial garden network. The 10 species selected for this program, include Lobelia, Helinium, Physotegia, Allium, Penstemon, Monarda and Aquilegia. Not included on the original plant list, Dr. Saxena is excited that he has since secured several native and exotic orchid species to add to the collection.

*Dendrobium spp.* in culture currently being used to develop orchid propagation technology.

Efficient production will be key to ensuring commercial success of these new varieties. Drawing on research results and resources made available through GRIPP, a variety of approaches will be utilized, including an expansion of research already underway to study the ability of indolamines compounds to enhance plant growth and survival. Optimized tissue culture propagation systems will improve mass production efficiency and cryopreservation techniques will help in biobanking of important genotypes of endangered and horticulturally important species.

As Dr. Saxena pointed out, despite its devasting impacts, the pandemic has brought a whole new focus to the importance of our homes and our gardens. “A look at the impact of COVID on home gardening shows the importance of ornamental horticulture. New varieties and especially those that meet our demand for ecologically sound plants will be important to drive the sector into the future.”

Organization: University of Guelph

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